Hot water supply device

ABSTRACT

A hot water supply device includes a heat exchanger, a temperature detection sensor detecting the surface temperature of the heat exchanger, and a fixing fitting fixing the sensor to a casing of the heat exchanger. The heat exchanger includes heat exchange tubing, a plurality of fins brazed to the heat exchange tubing, and the casing within which the tubing and the fins are housed, and to which both end portions of each of the fins are brazed. The fixing fitting includes a sensor fixing portion to which the temperature detection sensor is fixed, and fitting fixing portions attached to the casing. A predetermined gap is defined between the sensor fixing portion and the casing. The fitting fixing portions are brazed to an outer surface portion of the casing corresponding to the outside of a portion thereof where the casing and one or a plurality of the fins are brazed together.

BACKGROUND OF THE INVENTION

The present invention relates to a hot water supply device, and more particularly relates to such a device in which a construction is improved for attaching, to a heat exchanger casing, a temperature detection means that detects the temperature of the heat exchanger casing.

From the prior art, hot water supply devices of various types have been widely applied in general household use for provision of hot water, and these include gas hot water supply devices, electric hot water supply devices, fuel oil hot water supply devices, and so on. In particular, a gas powered hot water supply device is per se known comprising a blower fan that sucks in air for combustion from the exterior, a burner unit that mixes the combustion air with fuel gas and combusts the mixture, a heat exchanger that heats up cold water by exchanging heat between the combustion gas which is at high temperature and the cold water which flows in a heat exchange tubing, an exhaust pipe for discharging the exhaust to the exterior after heat exchange, and so on.

As the heat exchanger described above, a fin-and-tube type heat exchanger is generally applied that includes a heat exchange tubing made from copper and a plurality of fins also made from copper that are fixed to the heat exchange tubing so as to be capable of transferring heat thereto; and a temperature detection means that detects the temperature of the heat exchanger is also commonly provided (refer to Patent Document #1).

Now, when tap water whose hardness is high is employed as the supply of fresh water to the heat exchanger, scale is formed due to combination of calcium and/or magnesium or the like and carbonate ions and/or sulfate ions or the like contained in the tap water, and scale clogging takes place due to undesirable accumulation of this scale within the heat exchange tubing of the heat exchanger, so that the heat exchange efficiency of the heat exchanger is deteriorated. Moreover, when the hot water supply device is used over the long term, fin clogging may also occur due to soot adhering to the fins of the heat exchanger, and this also causes deterioration of the heat exchange efficiency of the heat exchanger.

If use of the hot water supply device is to be continued in the state in which scale clogging and/or fin clogging has taken place, then it is necessary to perform maintenance in order to remove the scale and/or the soot, since there is an anxiety of damage to the heat exchanger if an anomaly such as scale clogging or fin clogging has occurred. Due to this, in the prior art, a technique has been employed of detecting the temperature of the heat exchanger with a temperature detection means, and of detecting anomaly such as clogging by scale based on this detected temperature.

As related technology, in unpublished Japanese Patent Application 2014-108508, the applicant of the present application has proposed a sensor fixing fitting for attaching, to the front surface of the casing of a fin-and-tube type heat exchanger, a temperature detection means that detects the temperature of the front surface of the casing. As shown in FIG. 10, the sensor fixing fitting 100 comprises a holding plate portion 101, a fixing portion 102, a pressing portion 103, a signal line holding portion 104, and a pair of attachment lugs 105 and an engagement clip 106 that extend downward from the holding plate portion 101, all of which are made from thin stainless steel plate.

The heat exchanger 108 is disposed above the burner casing 107. And the sensor fixing fitting 100 is positioned in a position near the front surface of the casing 109 of the heat exchanger 108, and is fixed by the pair of attachment lugs 105 and the engagement clip 106 being engaged to an engagement portion 111 of a flange 110 of the casing 109. The sensor main body 121 of the temperature detection sensor 120 is disposed between the outer surface of the casing 109 and the pressing portion 103, and is pressed by the pressing portion 103 so as to be contacted against the outer surface of the casing 109. A positioning portion 122 of the temperature detection sensor 120 is fitted over a protruding lug 102 a of the fixing portion 102, so that the signal line 123 of the detection sensor 120 is held by the signal line holding portion 104.

Attention is drawn to Japanese Laid-Open Patent Publication 2015-114004 as a prior art document.

However when, on the assembly line for this hot water supply device, the above described temperature detection sensor is to be attached to the casing, the sensor fixing fitting is attached to the casing by hand, and the sensor is attached in the state in which the sensor main body is sandwiched between the outer surface of the casing and the pressing portion. At this time, in some cases, variation may occur between different production examples of the hot water supply device, even though they are of the same type, due to the fact that the pressure exerted by the pressing portion is not fixedly determined.

Since the temperature that is detected varies when the state of contact between the main body of the temperature detection sensor and the outer surface of the casing varies, accordingly error of the detection temperature of the temperature detection sensor may take place due to the variation described above of the pressure exerted by the pressing portion, and thus it is difficult to stabilize the temperature detection performance of the temperature detection sensor.

The object of the present invention is to provide a hot water supply device that is capable of ensuring the stability of the temperature detection performance of a temperature detection means.

SUMMARY OF THE INVENTION

The present invention presents a hot water supply device comprising a burner unit, a heat exchanger for applying heat to water with combustion gases supplied from the burner unit, a temperature detection means for detecting a surface temperature of the heat exchanger, and a fixing fitting for fixing the temperature detection means on the heat exchanger, characterized in that: the burner unit includes a plurality of combustion tubes disposed in a predetermined arranging direction, with the plurality of combustion tubes including at least one usual combustion tube that is always performing combustion while hot water being supplied; the heat exchanger comprises a heat exchange tubing through which hot water flows, a plurality of fins that are brazed to the heat exchange tubing, and a heat exchanger casing that houses the heat exchange tubing and the plurality of fins and to an inner surface of which both end portions of each of the plurality of fins are brazed; the heat exchange tubing comprises a plurality of straight pipe portions that extend in the arranging direction and that are arranged so as to be spaced apart at predetermined intervals in a direction orthogonal to the arranging direction, connected together by a plurality of U-shaped link tubes; the fixing fitting comprises a sensor fixing portion to which the temperature detection means is fixed, and a fitting fixing portion that are fixed to an outer surface of the heat exchanger casing; and along with a predetermined gap being defined between the sensor fixing portion and the outer surface of the heat exchanger casing, the fitting fixing portion is brazed to the outer surface of the heat exchanger casing that corresponds to an exterior portion where the heat exchanger casing and one or a plurality of fins are brazed together.

In a desirable first aspect of the present invention, the heat exchange tubing comprises a lower heat exchange tubing that is disposed so as directly to oppose the burner unit from above, and an upper heat exchange tubing that is disposed above the lower heat exchange tubing and that applies heat to hot water heated by the lower heat exchange tubing; and the fixing fitting is provided in a position on the outer surface of the heat exchanger casing so as to correspond to the most downstream side in the direction of hot water flow in the lower heat exchange tubing, and so as to correspond to the usual combustion tube.

In a desirable second aspect of the present invention, the fixing fitting comprises a projecting lug that projects upward from an upper edge of the fitting fixing portion.

In a desirable third aspect of the present invention, the fixing fitting comprises a pair of flanges that extend from both upper and lower edges of the sensor fixing portion, horizontally in a direction departing from the casing.

In a desirable fourth aspect of the present invention, a protective cover that protects the sensor fixing portion and the temperature detection means is attached to the fixing fitting via the pair of flanges.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rough structural diagram showing a hot water supply device according to an embodiment of the present invention;

FIG. 2 is an elevation view of a sensible heat exchanger and of a latent heat exchanger;

FIG. 3 is a horizontal sectional plan view showing a lower heat exchange tubing, a heat exchanger casing, and fins of the sensible heat exchanger;

FIG. 4 is a horizontal sectional plan view showing an upper heat exchange tubing, the heat exchanger casing, and fins of the sensible heat exchanger;

FIG. 5 is a perspective view of a fixing fitting that is attached to the outer surface of a casing of the sensible heat exchanger, and of a temperature detection sensor that is attached to the fixing fitting;

FIG. 6 is a perspective view of essential portions, showing a state in which the fixing fitting, a protective cover, and the temperature detection sensor are attached to the casing;

FIG. 7 is a perspective view of essential portions, showing a state in which the fixing fitting and the temperature detection sensor are attached to the casing;

FIG. 8 is a perspective view of the protective cover;

FIG. 9 is a perspective view of the fixing fitting; and

FIG. 10 is a figure corresponding to FIG. 5, relating to an unpublished prior art.

DETAILED DESCRIPTION

In the following, an embodiment of the present invention will be described with reference to the drawings. First, the overall structure of a hot water supply device 1 will be explained. The hot water supply device 1 is an apparatus that may be applied as a device for supplying heat to a hot water heating system or a room heating device or the like, and, as shown in FIG. 1, is built as a gas hot water supply unit that supplies hot water by utilizing heat generated by combustion of fuel gas for heating of cold or warm water.

This hot water supply device 1 comprises a blower fan 2 for supplying air for combustion, a burner section 3 for combusting fuel gas, a heat exchanger section 4 that exchanges heat between the combustion gases generated by the burner section 3 and cold water, an exhaust vent 5 that discharges the combustion gases after heat exchange by the heat exchanger section 4, conduits of various types such as a cold water intake pipe 6 a and a hot water output pipe 6 b and so on, a control unit 7 that receives signals from various sensors and controls the operation of devices of various types, and the like.

Next, the burner section 3 will be explained.

As shown in FIGS. 1 and 2, the burner section 3 comprises a burner unit 11 that mixes together and combusts fuel gas supplied from a fuel supply conduit (not shown) and combustion air supplied from the blower fan 2, a burner casing 12 that contains the burner unit 11, a combustion space 13 defined within the burner casing 12 above the burner unit 11, and so on. The burner casing 12 is formed in the shape of a rectangular parallelepiped, and is open at the top. The blower fan 2 is provided at the lower portion of the burner casing 12.

As shown in FIGS. 1 and 2, the burner unit 11 comprises a plurality of combustion tubes 11 a that are arranged in parallel so as to extend in the front to back direction and are disposed in sequence in a predetermined arranging direction (left to right direction); for example, the burner unit 11 may be built as a multi-stage unit having six combustion stages (i.e. combustion regions) #1 through #6, and combustion operation may be performed by changing over to one or more of the combustion stages #1 through #6, according to the required capacity for supply of hot water. The respective numbers of combustion tubes in each of the combustion stages #1 through #6 may, for example, be 2, 3, 5, 7, 12, and 17. Each of the plurality of combustion tubes 11 a is connected to a fuel supply conduit. Combustion operation by each of the combustion stages #1 through #6 is controlled by the control unit 7. It should be noted that, in normal conditions, the combustion stage which is most frequently used is the combustion stage #2. Three combustion tubes 11 a of the combustion stage #2 are usual combustion tubes that are always performing combustion while hot water being supplied.

As shown in FIG. 2, an igniter 15 and a flame rod 16 are provided in the combustion space 13 above the portion of the burner unit 11 that corresponds to the combustion stage #1. The igniter 15 and the flame rod 16 are attached to the front wall of the burner casing 12.

The igniter 15 is a device for igniting the fuel-air mixture gases supplied from the burner unit 11 by generating an ignition spark between itself and an ignition target that is provided to the burner unit 11, and is mounted so as to project into the combustion space 13 while extending obliquely downward.

The flame rod 16 is a device that applies a voltage to the flame during combustion operation of the burner unit 11; whether or not a flame is present is detected by detecting electrical current flowing from the flame rod 16 to the flame.

Next, the heat exchanger section 4 will be explained.

As shown in FIGS. 1 and 2, the heat exchanger section 4 comprises a sensible heat exchanger 17 that mainly recovers sensible heat from the combustion gases, a latent heat exchanger 19 that mainly recovers latent heat from the combustion gases (i.e. from the exhaust) after heat exchange by the heat exchanger 17, a lower casing 18 that houses a heat exchange tubing 25 and a plurality of fins 26 of the heat exchanger 17, an upper casing 20 that houses the latent heat recovery heat exchanger 19, and so on.

As shown in FIGS. 3 through 5, the lower casing 18 is built as a rectangular case, with a flange 21 at the lower end of the casing 18 and a flange 22 at the upper end of the burner casing 12 being connected together by caulking and/or by screws.

As shown in FIGS. 1 and 2, the upper casing 20 is formed in the shape of a rectangular parallelepiped, and has a tray 6 d at its bottom portion for retrieval of condensate (drained water) generated due to latent heat recovery and also an exhaust intake passage 24 that opens to its interior, and is also provided with an exhaust vent 5, at a lower left side surface portion of the upper casing 20 that corresponds to the front surface of the hot water supply device 1, for discharging the exhaust to the exterior of the hot water supply device 1 after heat exchange.

The lower end portion of the upper casing 20 and the upper end portion of the lower casing 18 are connected together by caulking and/or by screws. As shown in FIG. 2, a temperature fuse 23 that is capable of detecting anomalous high temperature is provided around the periphery of the lower portion of the casing 18, for detecting leakage of exhaust from the casing 18. The temperature fuse 23 is attached to the flange 21 by a plurality of fuse fixing fittings 23 a.

Next, the sensible heat exchanger 17 will be explained.

As shown in FIGS. 2 through 4, the sensible heat exchanger 17 is a fin-and-tube type heat exchanger that comprises the heat exchange tubing 25, a plurality of fins 26 that are fixed to the heat exchange tubings 25 so that heat can be transferred therebetween, and so on.

The heat exchange tubing 25 includes a lower heat exchange tubing 25A that is disposed in the lower portion of the sensible heat exchanger 17 and extends horizontally, and an upper heat exchange tubing 25B that is disposed in the upper portion of the sensible heat exchanger 17 and also extends horizontally. The lower heat exchange tubing 25A is formed by a plurality of straight pipes 27 a through 27 d that are connected together in series by U-shaped connection bends 28. And the upper heat exchange tubing 25B is formed by a plurality of straight pipes 27 e through 27 h that are connected together in series by other U-shaped connection bends 28.

The plurality of fins 26 of the sensible heat exchanger 17 are made as vertical thin plates having almost the same size in the vertical direction as that of the casing 18, and are arranged parallel to one another with small gaps being left between them in the horizontal direction. Flanges 26 a at the front and back end portions of the fins 26 are fixed to the inner surfaces of the front wall 18 a and of the rear wall 18 b of the casing 18 by brazing. The straight pipes 27 a through 27 h are arranged so as to pass through apertures formed in the plurality of fins 26, and the straight pipes 27 a through 27 h are brazed to the edges of these apertures in the plurality of fins. It should be understood that, although the heat exchange tubing 25 and the fins 26 are manufactured from copper, the material from which they are made is not necessarily limited; they could also be made from stainless steel, for example.

Together with fuel gas supplied to the burner unit 11 from the fuel supply conduit, air for combustion is also supplied from the blower fan 2, and the resulting fuel-air mixture gases in which the fuel gas and the air are mixed together is combusted in the combustion space 13. The combustion gases that is generated at this time is conducted upward from the combustion space 13 into the interior of the casing 18 and becomes cooler as it supplies heat to fresh water in the sensible heat exchanger 17, and then is exhausted from the casing 18 via the intake passage 24 and is conducted into the interior of the upper casing 20.

After cold water has been warmed by the latent heat recovery heat exchanger 19, it is supplied to the sensible heat exchanger 17 as shown by the arrow A in FIG. 3, and flows into the interior of the upper heat exchange tubing 25B after having flowed through the interior of the lower heat exchange tubing 25A, and this water is heated by the sensible heat of the combustion gases while passing through the sensible heat exchanger 17 as described above and becomes hot water, which is then sent out from the hot water output pipe 6 b to the exterior of the hot water supply device 1, as shown by the arrow B in FIG. 4.

Next, a temperature detection sensor 30 for detecting the temperature of the surface of the casing 18 (i.e. temperature detection means) and a fixing fitting 40 for attaching the temperature detection sensor 30 to a portion in the vicinity of the surface of the front wall 18 a of the casing 18 will be explained.

As shown in FIGS. 2 and 3, the fixing fitting 40 to which the temperature detection sensor 30 is attached is provided at a position that, among the various portions in the vicinity of the surface of the front wall 18 a of the casing 18, is a position that corresponds to a portion of the lower heat exchange tubing 25A of the heat exchange tubing 25, which directly opposes the upper side of the combustion space of the burner section 3, that is at the most downstream side in the flow direction of the hot water (i.e. the straight pipe 27 d), and that corresponds to the combustion region whose frequency of use for combustion operation is the highest (i.e. the combustion stage #2). This is in order to detect a temperature that reflects the temperature of the heat exchange tubing 25 at its location where the frequency of thermal load is the highest (i.e. at its location where most scale and/or soot accumulate).

As shown in FIGS. 5 through 9, the fixing fitting 40 comprises a sensor fixing portion 41 that is parallel to the front wall 18 a of the casing 18, a pair of left and right leg portions 42 a, 42 b, a pair of left and right fitting fixing portions 43 a, 43 b that are parallel to the front wall 18, a pair of left and right projecting lugs 44 a, 44 b, and a pair of upper and lower rotation prevention flanges 45 a, 45 b, and is formed from copper plate as an integral member.

The sensor fixing portion 41 is a portion that is adapted for the temperature detection sensor 30 to be attached to its outer surface, and is formed in the shape of a flat narrow rectangular plate that is long in the left to right direction. A screw hole 41 a is formed in the right end portion of the sensor fixing portion 41. The pair of left and right leg portions 42 a, 42 b are elements for defining a predetermined gap S between the sensor fixing portion 41 and the front wall 18 a of the casing 18, and they extend rearward for a predetermined length from the left and right end portions of the sensor fixing portion 41.

The pair of left and right fitting fixing portions 43 a, 43 b are elements by which the fixing fitting 40 is attached to the front wall 18 a of the casing 18 by brazing, and they project from the pair of left and right leg portions 42 a, 42 b towards their opposite sides from the sensor fixing portion 41. Moreover, the pair of left and right projecting lugs 44 a, 44 b are elements for setting the brazing filler material with their upwardly facing inclined surfaces, and they extend obliquely upward and forward from the upper edges of the pair of left and right fitting fixing portions 43 a, 43 b respectively.

The pair of upper and lower rotation prevention flanges 45 a, 45 b are elements for, when the temperature sensor 30 is attached with a screw 33, restraining the temperature detection sensor 30 so that it does not rotate, and also are for enabling a protective cover 50 that will be described hereinafter to be installed, and they project horizontally forward from the upper and lower edges of the sensor fixing portion 41.

The temperature sensor 30 is, for example, an element comprising a thermistor that is sealed in a sealing mass 30 a made from a ceramic material, with a position determination portion 31 made as an annular metallic plate being formed at its one end portion, while a harness 32 of a signal line extends leftward from its other end portion.

When the fixing fitting 40 is to be attached by brazing to the front wall 18 a of the casing 18, the fixing fitting 40 is held at a predetermined attachment position on the front wall 18 a by a jig not shown in the figures, the pair of fitting fixing portions 43 a, 43 b are held in the state of contacting against the front wall 18 a of the casing 18, some brazing filler material is set on the upwardly facing inclined surfaces of the pair of projecting lugs 44 a, 44 b, and, simultaneously with the junction portions between the heat exchange tubing 25 and the plurality of fins 26 of the heat exchanger 17 and the junction portions between the flanges 26 a at the front and rear ends of the plurality of fins 26 and the inner surface of the casing 18 and so on being brazed by brazing in a furnace, also the pair of fitting fixing portions 43 a, 43 b are fixed by the brazing filler material to the front wall 18 a of the casing 18 by brazing in the furnace.

After the brazing in the furnace has been completed, the temperature detection sensor is positioned in the state of being contacted against the outer surface of the sensor fixing portion 41, and its position determination portion 31 is fixed with a screw 33 to the sensor fixing portion 41.

Subsequently, the protective cover 50 is attached so as to cover the sensor fixing portion 41 and the temperature detection sensor 30. This protective cover 50 is an element for protecting the mass 30 of ceramic that seals over the temperature detection sensor 30.

The protective cover 50 comprises a flat plate portion 51 that coves over the front surface of the temperature detection sensor 30 from the front, a pair of engagement clips 52, 53 that extend rearward from the upper and lower edges of the flat plate portion 51, and a stopper portion 54 that extends rearward from the right edge of the flat plate portion 51, and is formed integrally from a thin plate made from stainless steel which is elastic.

The upper engagement clip 52 has an engagement claw 52 a at its rear end portion that is turned back forward and downward, and this upper engagement clip 52 extends rearwards along the upper surface of the upper flange 45 a, with its engagement claw 52 a being engaged with and clamped to the rear surface of the sensor fixing portion 41. Similarly, the lower engagement clip 53 has an engagement claw 53 a at its rear end portion that is turned back forward and upward, and this lower engagement clip 53 extends rearwards along the lower surface of the lower flange 45 b, with its engagement claw 53 a being engaged with and clamped to the rear surface of the sensor fixing portion 41.

In the state in which the fixing fitting 40 is fixed to the outer surface of the front wall 18 a of the casing 18 and the temperature detection sensor 30 is attached to the outer surface of the sensor fixing portion 41, a predetermined clearance S (for example, around 5 to 10 mm) is defined between the rear surface of the sensor fixing portion 41 and the outer surface of the front wall 18 a of the casing 18.

Next, the operation and the beneficial effects of the fixing fitting 40 and the temperature detection sensor 30 of the hot water supply device 1 will be explained.

The fixing fitting 40 has the sensor fitting portion 41 which is separated by the clearance S from the outer surface of the casing 18 and the fitting fixing portions 43 a, 43 b that are integrally connected to this sensor fixing portion 41, and the temperature detection sensor 30 is fixed to the outer surface of the sensor fixing portion 41, while the fitting fixing portions 43 a, 43 b are brazed to the outer surface of the casing 18.

Since the fitting fixing portions 43 a, 43 b are brazed to positions on the outer surface of the casing 18 which correspond to the outside of the brazed portions where one or a plurality of the fins 26 are brazed to the casing 18, accordingly heat is transferred from the heat exchange tubing 25 to the fitting fixing portions 43 a, 43 b via the one or a plurality of fins 26 and the casing 18, and the fitting fixing portions 43 a, 43 b are reliably heated up to a temperature that reflects the temperature of the heat exchange tubing 25 (i.e. to a temperature that is almost equal to the temperature of the heat exchange tubing 25). And, since the heat is transmitted from these fitting fixing portions 43 a, 43 b to the sensor fixing portion 41, accordingly the sensor fixing portion 41 is also reliably heated up to a temperature that reflects the temperature of the heat exchange tubing 25.

Since the predetermined clearance S is defined between the sensor fixing portion 41 and the outer surface of the casing 18, and the temperature detection sensor 30 is fixed to the outer surface of the sensor fixing portion 41, accordingly, while the state is maintained in which the temperature detection sensor is not in contact with the outer surface of the casing 18, still the temperature detection sensor 30 detects the temperature of the sensor fixing portion 41, which reflects the temperature of the heat exchange tubing 25. And it is possible to stabilize the temperature detection performance of the temperature detection sensor 30, since the heat transfer path that transfers heat from the heat exchange tubing 25 to the sensor fixing portion 41 via the one or a plurality of fins 26, the casing 18, and the fitting fixing portions 43 a, 43 b remains the same and does not vary between different ones of a plurality of examples of the same type of hot water supply device.

The fixing fitting 40 is provided at a position on the outer surface of the front wall 18 a of the casing 18 that corresponds to the straight pipe 27 d, which is the portion in the lower heat exchange tubing 25A of the heat exchange tubing 25 most toward the downstream side in the flow direction of the hot water that directly opposes the combustion space 13 of the burner section 3 from above, and that moreover corresponds to the combustion stage #2, which is the combustion region whose frequency of usage in combustion operation is the highest. In this manner, by attaching the fixing fitting 40 in a position that corresponds to the heat exchange tubing portion whose frequency of usage during combustion operation is the highest and whose thermal load is accordingly the highest, it is possible to detect a temperature that reflects the temperature of the heat exchange tubing portion whose thermal load is the highest.

Since clogging with scale can most easily occur in the heat exchange tubing portion where the thermal load is highest, and clogging of the fins can most easily occur in the vicinity of that portion, accordingly it becomes possible to estimate the state of accumulation of scale and/or soot at high accuracy using the temperature detected by the temperature detection sensor 30 described above.

Since the fixing fitting 40 has the fitting fixing portions 43 a, 43 b on the left and right sides of the sensor fixing portion 41, accordingly it is possible to attach the fixing fitting 40 to the casing 18 in a stable state. Moreover heat transference to the sensor fixing portion 41 is excellent, since heat is conducted to the sensor fixing portion 41 from the fitting fixing portions 43 a, 43 b on both sides.

Furthermore, since the locations where brazing is performed on both the inner surface and the outer surface of the casing 18 are kept as small as possible by brazing only the fitting fixing portions 43 a, 43 b of the fixing fitting 40 to the casing 18 without its sensor fixing portion 41 being brazed to the casing 18, accordingly it is possible to suppress thermal distortion of the casing 18, and thereby it is possible to prevent deterioration of the durability of the casing 18.

Next, examples in which the above embodiment is partially varied will be explained.

1) Since the protective cover 50 is not essential, it may be omitted.

2) The disclosed fixing fitting 40 has only been shown by way of example; for a person skilled in the art, the present invention could be implemented in formats in which various modifications are included in the above embodiment, and it should be understood that the present invention also includes such variant embodiments. 

1. A hot water supply device comprising a burner unit, a heat exchanger for applying heat to water with combustion gases supplied from the burner unit, a temperature detection means for detecting a surface temperature of the heat exchanger, and a fixing fitting for fixing the temperature detection means on the heat exchanger, characterized in that: the burner unit includes a plurality of combustion tubes disposed in a predetermined arranging direction, with the plurality of combustion tubes including at least one usual combustion tube that is always performing combustion while hot water being supplied; the heat exchanger comprises a heat exchange tubing through which hot water flows, a plurality of fins that are brazed to the heat exchange tubing, and a heat exchanger casing that houses the heat exchange tubing and the plurality of fins and to an inner surface of which both end portions of each of the plurality of fins are brazed; the heat exchange tubing comprises a plurality of straight pipe portions that extend in the arranging direction and that are arranged so as to be spaced apart at predetermined intervals in a direction orthogonal to the arranging direction, connected together by a plurality of U-shaped link tubes; the fixing fitting comprises a sensor fixing portion to which the temperature detection means is fixed, and a fitting fixing portion that are fixed to an outer surface of the heat exchanger casing; and along with a predetermined gap being defined between the sensor fixing portion and the outer surface of the heat exchanger casing, the fitting fixing portion is brazed to the outer surface of the heat exchanger casing that corresponds to an exterior portion where the heat exchanger casing and one or a plurality of fins are brazed together.
 2. A hot water supply device according to claim 1, characterized in that: the heat exchange tubing comprises a lower heat exchange tubing that is disposed so as directly to oppose the burner unit from above, and an upper heat exchange tubing that is disposed above the lower heat exchange tubing and that applies heat to hot water heated by the lower heat exchange tubing; and the fixing fitting is provided in a position on the outer surface of the heat exchanger casing so as to correspond to the most downstream side in the direction of hot water flow in the lower heat exchange tubing, and so as to correspond to the usual combustion tube.
 3. A hot water supply device according to claim 1, characterized in that the fixing fitting comprises a projecting lug that projects upward from an upper edge of the fitting fixing portion.
 4. A hot water supply device according to claim 1, characterized in that the fixing fitting comprises a pair of flanges that extend from both upper and lower edges of the sensor fixing portion, horizontally in a direction departing from the heat exchanger casing.
 5. A hot water supply device according to claim 4, characterized in that a protective cover that protects the sensor fixing portion and the temperature detection means is attached to the fixing fitting via the pair of flanges. 